An air/fuel mixture flows through the connecting piece from the carburetor to the combustion chamber during operation of the internal combustion engine. A portion of the fuel, especially long-chain hydrocarbons, deposits on the inner wall of the connecting piece and forms a fuel film. Fuel can also collect in the expansion fold of the connecting piece. When swinging the work apparatus, especially at idle, an enrichment of the mixture can occur because of fuel entrained from the connecting piece. A sudden mixture enrichment can lead to disturbances in the smooth running of the engine up to a stalling thereof especially in small work apparatus having a low mass moment of inertia.
A connecting piece between a carburetor and the combustion chamber is disclosed in U.S. Pat. No. 4,711,225. This connecting piece is made of elastic material and has an expansion fold. A guide ring is arranged in the region of the expansion fold in the carburetor-end section. The inner periphery of this guide ring passes seamlessly into the engine-end section. Knurling is provided in a region of the connecting piece which prevents the formation of an uninterrupted fuel film. In this way, the fuel film, which has deposited on the inner wall of the connecting piece, is prevented from suddenly reaching the combustion chamber.
It has, however, been shown that not only the fuel film, which has deposited on the inner wall, can lead to a sudden enrichment of the mixture but also fuel, which collects in the expansion fold, can suddenly be supplied to the combustion chamber and lead to a stalling of the engine.